Bicyclo-orthoester as a low-shrinkage additive in cationic UV curing

A commercially available bicyclo-orthoester (BOE) was used as, low-shrinkage additive for cationic UV curing of epoxy resins. A high reactivity of BOE by ring-opening homopolymerization has been observed under cationic UV curing conditions. The BOE and trimethylolpropane triglycidyl ether monomers are compatible and give rise to a cured copolymeric network, under UV irradiation, with a flexibilization increase by increasing the BOE content in the photocurable formulation. Shrinkage after photopolymerization shows a linear reduction by increasing the BOE content in the photocurable formulation; a volume expansion upon polymerization is reached in the presence of SO wt% of the additive. (c) 2007 Society of Chemical Industry